Challenges of welding of catalyst tubes and outlet assemblies in Hydrogen Reformers (original) (raw)
Related papers
Microstructural evaluation of welded fresh-to-aged reformer tubes used in hydrogen production plants
Engineering Failure Analysis, 2018
Heat resistant reformer tubes comprise a significant fraction of petrochemical reforming plants cost considering their high alloy content (i.e. 25Cr-35Ni-1Nb-0.1Ti). The bottom portion of tubes experiences the highest temperatures in the furnaces leading to microstructural changes, creep damage, and loss of elongation over their service life which in this case is twenty years. There is a cost-and time-driven motivation to only replace this portion of tubes by welding in contrast with replacing entire set of tubes which is the common industrial practice. However, welding new to aged tubes may lead to reliability issues due to difference in mechanical properties as a result of microstructural differences. In the current study, the microstructure and tensile properties of aged and new tubes have been evaluated in an effort to qualify the mechanical integrity of weldments. Welding trials are carried out to investigate the microstructure of the aged-to-new weldments and correlate it with the tensile properties (particularly elongation). Findings reveal that the heat affected zone of aged tubes is prone to micro-cracking of bulky primary carbides and incipient melting particularly at the inner surface where the root pass is applied. Adopting preheating for the root pass is effective in reducing carbide micro-cracking by decreasing cooling rate which assists in the accommodation of stresses generated by thermal contraction. Despite presence of carbide micro-cracks, tensile elongation is not severely affected as aged-to-new welds exhibit comparable and slightly higher elongation than aged base metals (above 4%). It is proposed that this is partially due to the orientation of micro-cracks in carbides. Further microstructural and tensile property results are presented and discussed.
Failure Analysis of Incoloy 800HT and HP-Modified Alloy Materials in a Reformer
Journal of Failure Analysis and Prevention, 2019
The main causes of creep failure in the pigtails and tubes made of high-temperature Incoloy 800HT and HPmodified alloy materials of two natural gas primary reformers operating at a petrochemical plant complex were studied. Optical emission spectroscopy, high-resolution optical microscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were performed to verify that creep was the prevailing failure mechanism in both cases. Creep was confirmed in both cases by the (massive) presence of intergranular voids (aligned in some cases) at the grain boundaries and cracks originating from the edge and longitudinal to the edge in some areas. Localized overheating due to burner flame impingement most likely accelerated the creep rate deformation for the HP-modified reformer tube material though the material surpassed its design life of 100,000 h. The findings substantiate that high priority should be placed on reformer burner management and ensuring the catalyst in the reformer tubes is packed optimally to avoid downstream flows issues in the outlet pigtails. These measures can serve to mitigate the effects of localized heating that can contribute to the failure of these components.
Engineering Failure Analysis, 2009
A welded manifold pipe in a primary steam reformer used to transport hydrogen gas at about 873°C developed leakage in the weld fusion zone after about 22,000 h of operation. Detailed microstructural characterization using various electron-optical techniques and mechanical property evaluation were employed to determine the cause of failure. Selection of pipe material and filler metal with relatively high Si contents in the presence of Nb was found to be the cause of failure. It is shown that this combination had promoted intergranular precipitation of the embrittling Ni 3 Nb 2 Si Laves phase in the weld fusion zone leading to loss of rupture ductility and associated cracking.
Journal of Advanced Joining Processes, 2020
This research aims to find an inexpensive solution for the problem of welding stainless steel. Cheaper grade stainless steel is popular in Southeast Asia. In this present study, weld bead shape, microstructure, mechanical properties and corrosion behavior of SUS 201 austenitic stainless steel weld joint through the GTA welding process with filler metal grade RE 310 SS are studied. Welding was undertaken under four different conditions with shielding gases at 100%Ar, 1%H 2 + 99%Ar, 3%H 2 + 97%Ar and 5%H 2 + 95%Ar were compared. The results gained from this investigation indicate that the weld joint mixtures of hydrogen with increased argon shielding gas showed no defects of the weld, increased weld bead size (slightly increased due to the welding speed increased in tandem), reduced delta-ferrite, decreased hardness and ultimate strength. However, the pitting corrosion area occurred at the interface between the delta-ferrite phase and the austenite phase because of low chromium in this region.
Process enhancement using hydrogen-induced shielding: H2-induced A-TIG welding process
Materials and Manufacturing Processes, 2020
Deeper penetration in a gas tungsten arc welding process is the essential requirement for the fabrication of duplex stainless steel pipes. Activated fluxes and associated activated tungsten inert gas' (A-TIG) welding process has proved itself as the better option for improved dilution and the deeper penetration. Use of hydrogen in shielding environment of A-TIG process for different ranges of activated fluxes needs to assess for deeper penetration and associated weld properties. Present investigation addresses the issue of deeper penetration using different activated fluxes in A-TIG process along with mixing of 2.5% H 2 in the argon gas shielding. An effect of H 2-induced shielding during CrO 3 , MoS 2 , TiO 2 , and SiO 2 fluxes in A-TIG process has been investigated with weld pool morphology, depth of penetration, weld chemistry, scanning electron microscopy, optical microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The extra heat produced due to activated fluxes in H 2-induced shielding have been quantify in the study. The decomposed oxygen in the weld pool reacts with hydrogen in shielding and enhances the arc density. The growths of ferrite and austenite grains as well as the dendrite arm spacing have been significantly affected due to the presence of H 2 in the shielding. Oxide-based fluxes with H 2-induced shielding could promote the arc constriction behavior and Peclet number with enhanced heat density.
Metals
This study presents a failure analysis in two reformer tubes used for hydrogen production in a petrochemical industry. These tubes (Tube A and Tube B) were made by the centrifugal casting of HP-Nb alloy in such a way that one contained titanium as a micro-element, and the other was free from titanium in its chemical composition. Although the two tubes were subjected to similar creep conditions, Tube A failed after only 46,000 h of operation against the design life of 100,000 h. SEM images showed initiation and growth of creep pores next to chromium carbide particles, as well as the formation of microcracks in Cr23C6 carbides. Pore initiation occurs as a result of grain boundary sliding and is strongly dependent on structural morphology. The tube containing titanium (Tube B) showed higher thermal stability and higher creep resistance than the tube without titanium (Tube A), which was due to the formation of finer and more discrete carbide particles. The final fracture of the tube wit...
Improve The Weld Quality By Reducing Hydrogen Cracking By Control Of Various Welding Parameters
Hydrogen cracking is one of the most common defects that get induced in the welding of the pipes or we can say that in pipeline welding. Here in this paper pipes are of X80 steels, the use of this steel had been come into picture since 1985 and it becomes very helpful in transporting oil and gases through long distances and effect and remedies of hydrogen cracking are discussed in order to obtain good weld characteristics in electric arc welding. To prevent cracking and to achieve high strength the X80 steels are made of ultra-low carbon, ultra-low sulphur, micro-alloying elements (niobium, vanadium and titanium) and molybdenum.